Diaphragm type fuel pump with lost motion pick-up



DIPHRAGM TYPE FUEL PUMP WITH LOST MOTION PICK-UP F'iled June l, 1965 J, GOLD ET AL.

Jan. 2, 1968 2 Sheets-Sheet l .1. GOLD ET AL 3,361,039

DIAPHRAGM TYPE FUEL PUMP WITH LOST MOTION PICK-UP Jan. 2,1968

'2 sheets-sneer a Filed June l, 1965 United States Patent O" 3,361,039 DIAPHRAGM TYPE FUEL PUMP WITH LOST MOTION PICK-Ul John Gold, Fiint, and Robert Gerald Taylor, Flushing,

Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed June 1, 1965, Ser. No. 460,060

` 2 Claims. (Cl. 92-140) This invention relates to pumps and more particularly to lost motion pick-up devices in diaphragm type fuel pumps which are particularly suitable for use in auto mobiles. This general type of pump is disclosed in the United States Patent 2,818,027 granted Dec. 31, 1957, in the names of W. E. Barnes and G. W. Harry. A pump of this type includes a pumping diaphragm adapted to be actuated in one direction by spring means to effect a pumping stroke and in the opposite direction by a pivoted lever or rocker arm in turn actuated by an extraneous element such as a cam of an internal combustion engine to perform a suction stroke.

A fuel pump of this nature, while serving an automobile engine, necessarily performs a dual function. It must not only pump fuel from the gas tank to the carburetor but must also act as a fuel regulator. In other words, when the carburetor is asking for fuel, the pump must supply it at a desired rate to satisfy the demand and must stop pumping or discharging any fuel in excess of the demand. This regulator function is customarily accomplished by the use of a lost motion pick-up arrangement in the pump actuator lever construction. When the carburetors fuel demand has been met, pick-up surfaces in the articulated lever construction or rocker arm separate and no exteriorly applied driving power is transmitted through the arm to the pump. When the carburetor once again demands fuel, the rocker arm pickup surfaces again make contact positively to transmit power for suction strokes only and the potential power in the pump. spring means is increased so that the pump will deliver the fuel required. This contacting or closing of the pickup surfaces is accompanied by a click often audi-ble above engine noise. This sudden closing often triggers noises in addition to the click referred to.

An object of the present invention is to provide an improved diaphragm type pump in which rocker arm operation is quiet in effecting pump discharge regulation.

A feature of the present invention is a diaphragm type fuel pump in which rocker arm articulation is such that power transmittal is accomplished by surfaces on the arm engaging or approaching each other at an acute angle.

This and other important feature of the invention will now be described in detail in the specification and then pointed out more particularly in the appended claims.

In the drawings:

FIGURE 1 is a part-sectional View of a fuel pump with an actuating cam and an automotive cam shaft, the pump structure embodying one form of the present invention, and the pump being at the top of its stroke and no pump driving power being applied;

FIGURE 2 is a view similar to that of FIGURE 1 but showing the pump parts as positioned intermediate the length of the pump stroke and upon the initiation of a power application or suction stroke;

FIGURE 3 is a view similar to that of FIGURES 1 and 2 but the parts in positions assumed near the end of a stroke during which power is applied to induce suction and to increase the power potential of the pump spring means;

FIGURE 4 is an enlarged sectional view looking in the direction of the arrows IV-IV of FIGURE 5;

FIGURE 5 is an enlarged view of parts shown in FIG- URE 3 as engaged to transmit power; and

3,361,039 Patented Jan. 2, 1968 FIGURE 6 is an exploded and perspective view of parts shown in FIGURES 4 and 5.

In FIGURES 1, 2, and 3, an automobile camshaft 10 is shown upon which is xed a cam 12 as conventionally utilized in automobiles for operating fuel pumps. A fuel pump body is depicted at 14 as having an aperture 16 traversed by a pin I8 and a flange 19 adapted to be fixed in sealed relation around a crankcase opening of an engine as is conventional. A rocker arm is pivoted on the pin 18 and comprises a lever portion 20 within the pump body I4 and a lever portion 22 which extends outwardly from the aperture 16 and engages the cam 12. The pump body I4 encloses a conventional pumping diaphragm 24 a movable portion of which is clamped between two plates 26 and 28 in turn connected rigidly to the lower end of a plunger 30. The upper end of the latter is apertured and retained over a hook end 32 of the lever portion 20 and an intermediate portion of the plunger is fixed to a flexible sealing diaphragm 34. A spring 36 acts between the pumping diaphragm 24 and the body 14 to actuate the diaphragm 24 in one direction-i.e.during pumping strokes as is well known in the art of automobile fuel pumps. A chamber 37 accommodates the pumping spring 36 and it is vented as at 39.

A second spring 40 is interposed between a shoulder 42 of the pump body 14 and a depending leg of a small T-shaped plate 44 which is attached by means of rivets 46 to the lever portion 22 and two spacer plates 50 and 52. A cross section of the lever portion 2.2 is of an inverted U-shape, The lever portion 22 also carries an upstanding projection or stop tab 54 useful only in the assembly of the pump and which has noparticular purpose insofar as the present invention is concerned. A bushing 56 surrounds the shaft I8 and serves as a bearing for the two lever portions 20 and 22. As stated above, one end 32 of the lever portion 20 is formed as a hook. The other end of the lever portion 20 has an arcuate end surface X of compound curvature, that is, a portion of the end surface is formed `with a radius a and another portion thereof is formed with a smaller radius c so that the two surface portions smoothly merge with the other surface portion being coaxial with the shaft 1S. The T-shaped piece 44 riveted to the lever portion 22 is formed with a concave surface Y having a radius b and in such a way that the facing surfaces X and Y (FIGURE 5) of the two lever portions 20 and 44 approach each other at an acute angle and are adapted to Contact before the piece 44 hits a shoulder 60 on the lever portion 20.

The important aspect of this invention is the relation of the two surfaces X and Y and the manner of their engagement to gain a practically noiseless pickup or power transfer from the cam 12 to the pumping diaphragm 24.

In FIGURE 1, no power is transferred from the lever portion 22 to the lever portion 20 as the surfaces X and Y are not in engagement and the demand for fuel is being adequately supplied from the pumping chamber by the slow expansion of the spring 36. The lever portion 22 is, however, kept in continuous contact with the cam 12 by means of the spring 40. As soon, however, as the supply of fuel being discharged becomes inadequate to supply the demand, parts of the pump assume the positions as shown in FIGURE 2 and rotation of the cam 12 causes the surface Y to approach the surface X at an acute angle of contact. In FIGURE 2, contact between the surfaces X and Y has been made but no pumping action or transfer of power has been effected. Rotation of the cam 12, however, pushes the arm of lever portion 22 downwardly as shown in FIGURE 3 and the surface Y, having already engaged the surface X, causes the lever portion Ztl to swing upwardly about the shaft 18 and effect a suction roke of the pump. Further rotation of the cam 12 permits the pumping stroke by virtue of the potential energy placed in the spring 36 during the suction stroke.

The acute angle of approach of the surfaces X and Y eliminates the click heard in conventional pumps and there is nothing critical about this angle except that it must be sufficiently acute in a given design to avoid the click but not so acute as to jam the surfaces together or require excessive cam lift.

We claim:

1. A diaphragm type fuel pump having a pumping diaphragm, a pump body with an aperture and a rocker arm, a pivot pin having an axis xed in position in said body and traversing said aperture, said rocker arm having articulated lever portions pivoted on said pin and extending from the latter in opposite directions, one of said lever portions being connected to the said pumping diaphragm for actuating the same in one direction, the other of said lever portions extending from said aperture, spring means acting against said pump body and urging said lever portions in opposite directions around said pivot pin axis and including a spring acting against said pumping diaphragm to move the latter in a direction opposite to said one direction, said lever portions having arcuate facing surfaces which, in a plane normal to said pin, approach each other at an acute angle, and the arrangement being such that a movement of said other lever portion is adapted to cause engagement of said surfaces at said acute angle and move said diaphragm in said one direction against said spring.

2. A fuel pump as set forth in claim 1, wherein said arcuate facing surfaces extend partially around said fixed pivot pin axis.

References Cited UNITED STATES PATENTS 1,893,217 1/1933 Babitch 74--53 1,994,743 3/1935 Anderson 123-90 2,139,347 12/1938 Babitch 103-150 2,532,905 12/1950 Hall 74--519 2,818,027 12/1957 Barnes et al 103-150 DONLEY I. STOCKING, Primary Examiner.

l/VILLAM L. FREEH, Examiner'. 

1. A DIAPHRAGM TYPE FUEL PUMP HAVING A PUMPING DIAPHRAGM, A PUMP BODY WITH AN APERTURE AND A ROCKER ARM, A PIVOT PIN HAVING AN AXIS FIXED IN POSITION IN SAID BODY AND TRAVERSING SAID APERTURE, SAID ROCKER ARM HAVING ARTICULATED LEVER PORTIONS PIVOTED ON SAID PIN AND EXTENDING FROM THE LATTER IN OPPOSITE DIRECTIONS, ONE OF SAID LEVER PORTIONS BEING CONNECTED TO THE SAID PUMPING DIAPHRAGM FOR ACTUATING THE SAME IN ONE DIRECTION, THE OTHER OF SAID LEVER PORTIONS EXTENDING FROM SAID APERTURE, SPRING MEANS ACTING AGAINST SAID PUMP BODY AND URGING SAID LEVER PORTIONS IN OPPOSITE DIRECTIONS AROUND SAID PIVOT PIN AXIS AND INCLUDING A SPRING ACTING AGAINST SAID PUMPING DIAPHRAGM TO MOVE THE LATTER IN A DIRECTION OPPOSITE TO SAID ONE DIRECTION, SAID LEVER PORTIONS HAVING ARCUATE FACING SURFACES WHICH, IN A PLANE NORMAL TO SAID PIN, APPROACH EACH OTHER AT AN ACUTE ANGLE, AND THE ARRANGEMENT BEING SUCH THAT A MOVEMENT OF SAID OTHER LEVER PORTION IS ADAPTED TO CAUSE ENGAGEMENT OF SAID SURFACES AT SAID ACUTE ANGLE AND MOVE SAID DIAPHRAGM IN SAID ONE DIRECTION AGAINST SAID SPRING. 